Textbook Question
What is the main structural difference between d. cellulose and chitin?
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Ch. 20 - The Organic Chemistry of Carbohydrates
Bruice8th EditionOrganic ChemistryISBN: 9780135213711
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Table of contents
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 1)31
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 2)65
- Ch. 2 - Acids and Bases: Central to Understanding Organic Chemistry84
- Ch. 3 - An Introduction to Organic Compounds:Nomenclature, Physical Properties, and Structure183
- Ch. 4 - Isomers: The Arrangement of Atoms in Space121
- Ch. 5 - Alkenes: Structure, Nomenclature, and an Introduction to Reactivity • Thermodynamics and Kinetics83
- Ch. 6 - The Reactions of Alkenes • The Stereochemistry of Addition Reactions175
- Ch. 7 - The Reactions of Alkynes • An Introduction to Multistep Synthesis119
- Ch. 8 - Delocalized Electrons: Their Effect on Stability, pKa, and the Products of a Reaction • Aromaticity and Electronic Effects: An Introduction to the Reactions of Benzene148
- Ch. 9 - Substitution and Elimination Reactions of Alkyl Halides212
- Ch. 10 - Reactions of Alcohols, Ethers, Epoxides, Amines, and Sulfur-Containing Compounds131
- Ch. 11 - Organometallic Compounds60
- Ch. 12 - Radicals90
- Ch. 13 - Mass Spectrometry; Infrared Spectroscopy; UV/Vis Spectroscopy62
- Ch. 14 - NMR Spectroscopy95
- Ch. 15 - Reactions of Carboxylic Acids and Carboxylic Acid Derivatives123
- Ch. 16 - Reactions of Aldehydes and Ketones • More Reactions of Carboxylic Acid Derivatives141
- Ch. 17 - Reactions at the Alpha-Carbon101
- Ch. 18 - Reactions of Benzene and Substituted Benzenes144
- Ch. 19 - More About Amines • Reactions of Heterocyclic Compounds49
- Ch. 20 - The Organic Chemistry of Carbohydrates80
- Ch. 21 - Amino Acids, Peptides, and Proteins57
- Ch. 22 - Catalysis in Organic Reactions and in Enzymatic Reactions35
- Ch. 23 - The Organic Chemistry of the Coenzymes—Compounds Derived from Vitamins1
- Ch. 28 - Pericyclic Reactions58
Chapter 21, Problem 32
Explain why the C-3 OH group of vitamin C is more acidic than the C-2 OH group.
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Identify the structure of vitamin C (ascorbic acid) from the image. It contains a six-membered ring with hydroxyl groups at positions C-2, C-3, and C-5, along with a lactone group at C-1 and a double bond between C-2 and C-3.
Understand the concept of acidity in organic molecules. Acidity is influenced by the ability of the molecule to stabilize the negative charge on the conjugate base after deprotonation. This stabilization can occur through resonance, inductive effects, or hydrogen bonding.
Analyze the C-3 OH group. When the proton is removed from the C-3 OH group, the resulting conjugate base can delocalize the negative charge through resonance with the adjacent double bond between C-2 and C-3. This resonance stabilization makes the C-3 OH group more acidic.
Compare the C-2 OH group. When the proton is removed from the C-2 OH group, the resulting conjugate base does not benefit from resonance stabilization because the negative charge cannot delocalize effectively into the ring system. This makes the C-2 OH group less acidic.
Conclude that the C-3 OH group is more acidic than the C-2 OH group due to the resonance stabilization of its conjugate base, which is not available for the C-2 OH group.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Acidity and pKa
Acidity in organic chemistry refers to the tendency of a compound to donate a proton (H+). The strength of an acid is often measured by its pKa value; lower pKa values indicate stronger acids. In the context of vitamin C, the C-3 OH group is more acidic than the C-2 OH group, which can be attributed to the stability of the resulting conjugate base after deprotonation.
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Identifying pKa values
Resonance Stabilization
Resonance stabilization occurs when a molecule can be represented by multiple valid Lewis structures, allowing for the delocalization of electrons. In vitamin C, the conjugate base formed from the C-3 OH group can be stabilized by resonance with the adjacent carbonyl group, making it more favorable for the C-3 OH group to lose a proton compared to the C-2 OH group, which lacks similar stabilization.
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03:43The radical stability trend.
Inductive Effect
The inductive effect refers to the electron-withdrawing or electron-donating effects of substituents on a molecule, influencing acidity. In vitamin C, the presence of electronegative atoms or groups near the C-3 OH group can enhance its acidity by stabilizing the negative charge on the conjugate base through inductive withdrawal of electron density, further contributing to the greater acidity of the C-3 OH group compared to the C-2 OH group.
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01:47Understanding the Inductive Effect.
Related Practice
Textbook Question
Refer to Figure 20.5 to answer the following questions: b. People with type AB blood can receive blood from anyone, but they cannot give blood to everyone. To whom can they not give blood?
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Textbook Question
What is the main structural difference between c. amylopectin and glycogen?
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Textbook Question
What product or products are obtained when D-galactose reacts with each of the following?
b. Ag+, NH3, HO-
569
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Textbook Question
Refer to Figure 20.5 to answer the following questions: a. People with type O blood can donate blood to anyone, but they cannot receive blood from everyone. From whom can they not receive blood?
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Textbook Question
What is the main structural difference between b. amylose and amylopectin?
1149
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